The present invention relates to developing devices for use in electrophotographic printing devices, such as copying machines, printers, and facsimiles, and also to printing devices incorporating such a developing device and charging methods through contact for use in such developing devices.
A typical electrophotographic image forming device (electrophotographic device), such as a copying machine, a printer, or a facsimile, includes an LSU, a photosensitive drum, and a developing device. The LSU shines a laser on the rotatable photosensitive drum to form an electrostatic latent image on the surface of the photosensitive drum. The developing device supplies toner to the photosensitive drum to develop (visualize) the electrostatic latent image.
Equipped with a developing roller positioned side by side to the photosensitive drum, the developing device is adapted to gradually apply toner to the entire electrostatic latent image on the photosensitive drum by supplying toner to the surface of the developing roller and rotating the developing roller in a reverse direction to the photosensitive drum.
In this kind of developing device, the toner is electrostatically attracted to the electrostatic latent image on the photosensitive drum to develop the image. To realize this, the toner must be charged by one method or another.
For example, a developing device using non-magnetic, single-component toner is provided with a supply roller located opposite to the developing roller and a layer-thickness-restricting blade (blade) located downstream to the supply roller (downstream with respect to the direction of rotation of the developing roller) as shown in FIG. 29.
The supply roller gradually supplies toner to the surface of the rotatable developing roller, and the blade restricts the thickness of the toner layer formed by strings of toner particles standing on the developing roller. Also, the blade is adopted to rub the toner on the developing roller to charge the toner. In this manner, the toner used in the development is charged.
The charging method is employed not only in developing devices using single-component non-magnetic toner, but also in those using single-component magnetic toner (toner containing magnetic particles).
Another example is a developing device using a double-component developing agent containing toner and carrier, in which the toner and carrier are agitated and mixed in a toner vessel before they are supplied to the developing roller as shown in FIG. 30. The toner is charged by means of friction developing between them, similarly to the previous example.
Nevertheless, the configuration in which toner is charged by means of friction (mechanical rubbing) with a blade requires a great difference in speed between the toner and the blade to sufficiently charge the toner. A result is mechanical/thermal load being imposed on the toner and the blade in direct proportion to the speed difference.
If the speed difference is made greater to sufficiently charge the toner, the mechanical/thermal load on the toner and the blade increases too. This leads to such problems that the toner deteriorates or is damaged, particularly, in terms of charging properties. Another potential drawback is that the toner, having softened due to frictional heat (rubbing heat), fuses with the blade, the developing roller, etc., to cause the developing device to malfunction.
The other configuration in which toner is charged by means of friction with carrier, similarly to the first configuration, requires high speed agitation, as well as a great difference in speed between the toner and the blade, to sufficiently charge the toner. The toner and the carrier are hence put under excessive mechanical/thermal load. This again leads to such problems that the toner deteriorates, particularly, in terms of charging properties or the toner and the carrier are damaged. Another potential drawback is that the toner, having softened due to frictional heat, fuses to the carrier to degrade toner quality and thus image quality.
As detailed in the foregoing, it can be safely concluded that the developing device in which the toner is charged by means of friction between the toner and the blade or carrier has such a shortcoming that the toner, blade, carrier, and developing device itself are subject to damage.
The present invention has an objective to offer such a developing device that the toner and the device itself deteriorate only to a limited extent.
In order to achieve the objective, the developing device in accordance with the present invention is a developing device for visualizing an electrostatic latent image held and transported on the latent image carrier and includes:
a charged member for developing an electrostatic latent image to a visual image;
a charging section for charging the charged member through contact; and
an irradiation section for shining light onto the charging section to charge the charged member by means of the light shone.
In other words, in this developing device, the charged member for developing an electrostatic latent image into visual image is caused to contact the charging section and the irradiation section to shine light onto the charging section to charge the charged member.
In this case, since the charged member is charged by means of light shone by the irradiation section onto the charging section, there is no need to charge the charged member by means of rubbing of the developing roller with the layer-thickness-restricting blade. Therefore, the stress experienced by the charged member due to mechanical rubbing is suppressed, and deterioration of the charged member becomes preventable. Besides, the arrangement can prevent the charged member from fusing with the charging section (the developing roller, the layer-thickness-restricting blade, etc.) due to rubbing heat. Reliability in the developing device thus improves.
Alternatively, the developing device in accordance with the present invention (the present developing device), in order to achieve the objective, may be a developing device, for use in an electrophotographic device, for developing an electrostatic latent image on a latent image carrier with charged developing material and includes:
a charging section including charging material radicalized under light irradiation; and
a light irradiation section for irradiating light onto the charging section,
wherein
the device is specified to charge the developing material by causing the radicalized charging material to contact the developing material.
The present developing device is a developing device for use in a copying machine, printer, facsimile, or other electrophotographic printing device, to develop an electrostatic latent image with toner, ink, or other developing material. Here, the electrostatic latent image refers to an image produced on a photosensitive body or paper (recording paper) according to a potential distribution.
Further, the present developing device is specified to charge the developing material used in the development of an electrostatic latent image, so as to develop it in a satisfactory manner.
Especially, the present developing device includes: a charging section composed of charging material radicalized under light irradiation; and a light irradiation section for shining light onto the charging section. The present developing device is specified to charge the developing material by causing the radicalized charging material to contact the developing material.
Here, radicalizing charging material refers to turning the charging material into radicals (reactive active species) by exciting it and thus changing it in structure. In other words, the charging material is activated on molecular levels and changed into radicals which is an isomer.
The radical is a strong oxidizer and removes an electron from material that comes into contact with it. The radicalized charging material is specified to remove electrons from developing material that comes into contact and thus charge the developing material to a desired charge level.
The present developing device is specified in this manner so that the charging material is radicalized under light irradiation and used to charge the developing material.
Hence, in the present developing device, the developing material can be charged without experiencing frictional forces; therefore, the developing material is prevented from deteriorating due to frictional heat, and so is the device from becoming dirty with the developing material that has softened due to frictional heat.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.